Internal conduit coating method and apparatus



L. W. GREEN June 26; 1962 INTERNAL CONDUIT COATING METHOD AND APPARATUSFiled March 24, 1959 INVENTOR. dam/0 M 5?:[4/

United States Patent r 3,041,204 INTERNAL CONDUET COATING METHOD ANDAPPARATUS Leland W. Green, Malibu, Calif. (1710 Santa Monica Blvd, SantaMonica, Calif.) Filed Mar. 24, 1959, Ser. No. 801,631 4 Claims. (Cl.117-97) This invention relates to method and apparatus for coating theinner surface of pipes or conduits with any desired fluid material suchas sealing and caulking compositions, rust and corrosion inhibitors,paint, or the like. My device and process are particularly adapted foremployment in rigid conduits which are too long for conveniently passingtherethrough a cable-attached pipe-contacting head and hence resort hasbeen had in the past to various plug-type heads which are in effectblown through the conduit by air pressure. These have provenunsatisfactory in various ways, especially in becoming wedged in bendsor against minor projections of the conduit wall, as well as beingdiflicultly adjustable to variations in pipe diameter. In addition tothe diificulty of dislodging them when stuck, there is the furtherresult that even when these heads pass through, such obstructions orvariations along the pipe surface will affect the uniform thickness andcoverage of coating material spread by the contact heads; in fact, ifthey pass through too easily, considerable areas of conduit may not becoated at all.

Accordingly it is an object of the present invention to provide animproved device and method-for applying coating material to innerconduit surfaces, so as to. produce a more uniform film coat in aquicker and more satisfactory manner.

Another purpose resides in the provision of a fluidpropelled, deformablecontact head of novel construction, particularly adapted to negotiatebends in the line and pass other obstructions. In addition, should mycontact head become lodged in the line, as by an impassable obstruction,it is more readily dislodged and its direction more readily reversed forwithdrawal than is the case with conventional fluid-propelled, plug-typeheads.

A further advantage resides in the provision of means for balancing theinner pressure of my deformable contact head against pressure of thepropelling fluid, and of selectively varying the difference between thetwo pressures to adapt to various operating conditions, includingreversal of the direction of flow, such changes being effected by meansof air compression and release mechanisms connected along the conduit.

Yet another advantage arises from employment of different types ofspecial purpose, deformable conduit-engaging spheres which may beinterchangeably coupled to a novel connector member. In particular, theimmediate coating driving sphere of one form of my assembly is formedwith a peripheral band of axially-directed metering grooves which spreadparallel ribbons of coating material along the inner conduit face. Thefollowing sphere, coupled to the pressurized metering sphere by aconnector shaft so as to resemble a dumbbell, is a smoothing or wipingsphere which by its contact with the conduit face spreads out and mergesthe coating ribbons so as to form a continuous uniform film.

Other objects and advantages of the invention will be apparent from thefollowing description and claims, the novelty consisting in the featuresof construction, combination of parts, the unique relations of themembers and the relative prop'ortioning, disposition, and operationthere of, all as more completely outlined herein and particularlypointed out in the appended claims.

In the drawings, which form part of the present specification:

3,041,204 Patented June 26, 1962 FIG. 1 is a vertical longitudinalsectional view taken through a conduit section being internally coatedby fluid moved between two pairs of my deformable spheres shown inelevation, with the lead sphere seen entering an enlarged section ofconduit at the right, and particularly showing how its outer contactingsurface adjusts itself to the increased inner circumference of the pipe;

FIG. 2 is an enlarged perspective view of the rear driving pair ofspheres shown in FIG. 1, particularly showing the metering grooves aboutthe lead sphere of the pair;

FIG. 3 is a longitudinal section taken through a bend or curved portionof a conduit, particularly showing how a pair of my spheres, seen inelevation, accommodate themselves to pass the bend; and

FIG. 4 is a vertical axial section through one of a connected pair of myspheres which is adapted to be filled with pressurized air, withportions shown in elevation.

The conduit 10 illustrated in FIG. 1 represents a rigid pipe, such as apetroleum pipeline which may be laid across sections of the countrybetween successive pumping stations (not shown) disposed along the line,from which stations the flow of fluid through successive sections of theconduit may be controlled. From time to time it may be desirable toclean out one or more of such sections and recoat its inner surface.Accordingly air (or other gas) is supplied to the line from a suitablesource, such as pump 12, through an inlet line 14 and pressure regulator16 to a section of the conduit which is sealed off from the precedingsection as by a diaphragm or apertured disk plug 18. Adjacent thefurther terminal of the section, a similar annular closure 20 isprovided with air outlet 22 and flow regulator 24 by which the outflowof fluid from the conduit section ahead of the traveling coatingassembly can be regulated; or conversely a back-pressure may he built upthereagainst. Alternately, in the event of an insurmountable stoppage ofthe coating assembly in the conduit, due to an obstruction in the line,a reversing pressure can be built up by blowing air in through the line22.

Essentially my process comprises moving a body of liquid or semi-fluidcoating material 26 axially along the conduit while it is containedbetween two pairs of my deformable spheres 28, 30 the whole beingpropelled or driven by the rearward pair which in turn is activated byair pressure. Accordingly coating material 26 is moved along the innerface of the conduit, the volume of coating material thus held betweenthe two pairs of spheres gradually diminishing as it is spread along thepipe until the two pairs of compacting spheres approach each otherwithin the line. a

The spheres of the pair 30 particularly illustrated in FIGS. 3 and 4,are connected to provide an'essentially dumbbell-shaped unit whichconsists of a front element 32 and a rear element 34, each of which ishollow and her or rod 36 here shown as of rigid construction andhexagonal in transverse section. The connector is formed 'at each endwith a threaded end portion'38 of reduced cross section which is mountedin an internally threaded metal insert 39 to which the elastomericmaterial of the sphere is bonded. The connector 36 is provided'with twostepped cylindrical faces 40, 41 inwardly of the threaded end portion38, the latter-being bounded at its inner end by a shoulder 42. Anannular flange 44 mounts on the connector in abutting relation with theshoulder and provides a semi-spherical inner face 45 provided with aribor ridge 46 adapted to seat in the outer face of the sphere. A seal48 of the O-ring type completes the assembly. The connector can thus beinterchangeably of pipe length must be constant.

3 coupled at either end to any one of the spheres, thus perrnittingcomparative ease of replacement or substitution of one spherical unitfor another.

Diametrically opposite the mounting of the connector tube, each sphereis provided with another annular internally threaded insert 50 mountedin the wall of the sphere, the material of the sphere being bonded tothe peripheral surface of the insert. A valve body 52 formed by anexternal head or flange portion 54 provided with hexagonally disposedflat surfaces for engagement by a wrench, and an inwardly projectingtubular portion 56 carrying a shorter, externally threaded collar 58 isthreadedly mounted in the insert 50. Adjacent the body flange 54, anannular abutment shoulder 60 of somewhat restricted diameter is disposedin lateral registration with an aluminum crush washer so as to press itagainst the outer face of the ball-mounted insert 50 by tightening thevalve body. Within a tapped, centrally apertured, outwardly projectingexternally threaded nipple 64, there is threadedly mounted aconventional valve unit 66 (similar to that used in a pneumatic tire)the release pin 8 projecting outward and being receivable in a closurecap 70 (FIG. 1).

As seen particularly in FIGS. 1' and 2, the driving pair of spheres ordriving unit 28 is constructed of a forward pressurized sphere 76 and arear unpressurized sphere 78 secured together by a connector rod 84which may be of the same construction as the rod 36 previouslydescribed. The interior of sphere 78 has its hollow interior open to theatmosphere of the conduit through one or more openings 80.

The lead sphere 76 is designed to perform a metering function being forthat purpose provided with a peripheral band of axially aligned,parallel slots or grooves 86 extending for a short distance along thatportion of the sphere which even when somewhat deformed by pressure ofthe conduit thereagainst, presses against the inner face of the conduituniformly about the circumference. Consequently the coating material 26flows rearwardly through each groove as the sphere is blown forward, thedepth of coating material passed through each groove corresponding tothe channel depth of the grooves which in turn is regulated by theinternal pressure in the sphere. In this connecton, sphere 76 may beconstructed generally the same as the spheres 32 and 34. The followingor trailing sphere 78 performs a smoothing or trowelling action inflowing together the adjacent ribbons of coating composition so asuniformly to cover the entire inner face of the conduit. It will beapparent of course that the amount of pressure in the metering sphere 76must be balanced against the wiping force of the following sphere, thatis, the latter must not be so collapsible or inelastic as to fail towipe the entire pipe circumference. For this reason, a steel expansionband may be disposed within the sphere, although this is not shown.

In the operation of the pipe coating apparatus, a body of coatingmaterial 26 is initially trapped between the two units or assemblies 28,30, and air or other gas is supplied under pressure behind the drivingunit 28 to propel the entire train forward. Escape of air from the pipeahead the leading or driven unit 30 is controlled by the valve 24.

The factors involved in the control of the processes are: velocity ofthe train through the pipe; drive pressure; control or back pressure;pressure exerted on coating material; diameter of pipe; friction;viscosity of coating material; and internal pressure in sphericalelements.

Of the above factors viscosity can be considered constant. The pipediameter may be variable and the friction will be variable. The factorsof drive pressure and back pressure are controllable while the internalpressure in the spheres is preselected to suit the conditions to beencountered.

In order to attain uniform coating thickness, the amount of materialmetered by sphere 72, per increment The amount of coating material sometered is proportional to the pressureon the 4. coating material andthe increment of pipe length is a function of the velocity of the train,therefore these two factors must be kept constant, or if variationsoccur, compensation effects must be introduced. The velocity isproportional to the drive pressure minus the back pressure but isinfluenced by the unknown friction factor. The pressure on the coatingmaterial is equal to the drive pressure minus the friction of units 28.Control of these parameters is accomplished by the pressure regulator 16in the inlet line to maintain the drive pressure at a fixed value, whileback pressure gas is vented through flow regulator 24 which passes acertain volume at a given rate irrespective of the pressure.

A functional analysis of the system under various operational conditionsfollows:

Case I .--Sm00lh Conduit of Constant Diameter Friction will be constant;drive pressure is regulated and constant, therefore the velocity isconstant. As a result of the latter being constant, back pressure willbe constant as will the pressure on the coating material, hence thecoating will be of constant thickness.

Case 2.Obstructi0n in the Line As spheres 32 and 34 respectively meetthe obstruction, the velocity is abruptly reduced and consequently theback pressure drops. The pressure regulator 16 maintains the drivepressure at original value and the pressure on the coating fluidincreases, since friction is reduced by decrease in velocity. This willresult in greater compressive force on sphere 76 forcing it outwardagainst the conduit wall, with a consequent squeezing of the meteringnotches 86 on its periphery; thus a reduction in the amount of coatingmaterial compensates for reduced velocity. Also since the back pressureis decreasing, the net pressure or differential or driving force acrossthe train increases. This action continues until the spheres 32, 34 areforced past the obstruction after which the velocity will be restored,the regulators will react and the system returns to normal.

When unit 28 meets the obstruction, the velocity will again be reduced,back pressure will drop as a consequence of the flow regulator actionresulting in a reduction of pressure on the coating fluid. Meteringrequirements under these circumstances are self-compensating sincereduced coating material demand because of lower velocity is offset bythe reduction of pressure on the coating fluid. The reduction of backpressure and hence pressure on the coating material provides anincreased driving force across unit 28 to ultimately force it past therestriction after which equilibrium will be restored as before.

Case 3.Transiti0n From Smooth to Rough Conduit The analysis of thiscondition parallels that given under case 2 except that the reactionswill be of less magnitude and when equilibrium is established the backpressure will be lower to compensate for increased friction in therougher pipe.

Case 4.Transition to Conduit of Slightly Different Diameter As spheres32 and 34 successively enter the larger section they will expand intothe increased diameter, and continue to bear against the wall, but withless force, the friction force will consequently be reduced. Since thedisplacement is greater in the larger diameter back pressure willincrease since the flow regulator 24 will allow only a fixed rate. Thiscompensates for the change in friction factor and since the drivepressure is constant, no change in velocity will occur.

When sphere 76 encounters the larger section it will also expand andfurther reduce friction, but any increase in velocity will be offset byan increase in back pressure. The expansion of sphere 76 will cause acorresponding widening of the metering slots to supply additionalcoating material for the larger circumference and constant coatingthickness is maintained.

The action of the train encountering a section of reduced diameter wouldresult in converse compensating effects.

I claim:

' l. A conduit-coating device, comprising a'pair of resilient hollowspheres adapted to be moved along the interior of a conduit in slidingregistration with its inner perimeter and thus propel an adjacentquantity of coating material ahead of it through the conduit so as tocoat the same, said spheres being axially spaced apart by a radiallyrestricted connector member, one of said spheres being formed with aperipheral series of generally axially directed grooves disposed aboutits conduit-contacting circumference so as to meter ribbons ofconduit-adhering coating material therethrough, said one of said spheresbeing constructed and arranged for receiving and holding pressurizedfluid in its hollow interior. I

2. The device of claim 1 in which said other sphere has its interioropen to the conduit atmosphere so as to serve as a spreading agent forthe coating ribbons.

3'. A conduit-coating device, comprising a hollow, inflated, resilientsphere adapted to be moved along the interior of a conduit in slidingengagement therewith and to propel ahead of it a quantity of coatingmaterial, said sphere being formed with a peripheral series of axiallydirected grooves disposed evenly about the conduit-contacting surface, atrailing spreader member behind said sphere,

and said spreader member.

and a connector member extending between said sphere 4. The method ofcoating the interior of a conduit,

which comprises entrapping a fluid body between a first pair ofresilient, spaced and connected hollow, conduitengaging'spheres, and asecond pair of resilient, spaced and connected, hollow conduit-engagingspheres, providing and maintaining internal pressure in the spheres ofsaid first pair and the leading sphere of said second pair, moving saidpairs of spheres and said fluid body by applying fluid pressure behindsaid second pair, and maintaining back pressure against the leadingsphere of said first pair by providing a closure in the conduit ahead ofthe leading sphere and venting air from the space in the conduit betweenthe leading sphere and the closure at a constant rate of flow.

References Cited in the file of this patent UNITED STATES PATENTS1,485,577 Witten Mar. 4, 1924 1,703,463 Weigel Feb. 26, 1929 1,746,071Cotton Feb. 4, 1930 1,796,338 Moore Mar. 17, 1931 2,106,004 Inglee Jan.18, 1938 2,445,645 Stephens July 20, 1948 2,480,358 Curtis et a1 Aug.30, 1949 2,851,061 Bernard et a1. Sept. 9, 1958 FOREIGN PATENTS 381,307Great Britain Oct. 6, 1932

4. THE METHOD OF COATING THE INTERIOR OF A CONDUIT, WHICH COMPRISESENTRAPPING A FLUID BODY BETWEEN A FIRST PAIR OF RESILIENT, SPACED ANDCONNECTED HOLLOW, CONDUITENGAGING SPHERES, AND A SECOND PAIR OFRESILENT, SPACED ENGAGING SPHERES, AND A SECOND PAIR OF RESILIENT,SPACED AND CONNECTED, HOLLOW CONDUIT-ENGAGING SPHERES, PROVIDING ANDMAINTAINING INTERNAL PRESSURE IN THE SPHERES OF SAID FIRST PAIR AND THELEADING SPHERE OF SAID SECOND PAIR, MOVING SAID PAIRS OF SPHERES ANDSAID FLUID BODY BY APPLYING FLUID PRESSURE BEHIND SAID SECOND PAIR, ANDMAINTAINING BACK PRESSURE AGAINST THE LEADING SPHERE OF SAID FIRST PAIRBY PROVIDING A CLOSURE IN THE CONDUIT AHEAD OF THE LEADING SPHERE ANDVENTING AIR FROM THE SPACE IN THE CONDUIT BETWEEN THE LEADING SPHERE ANDTHE CLOSURE AT A CONSTANT RATE OF FLOW.